Shifting bits in a byte

BlitzMax Forums/BlitzMax Beginners Area/Shifting bits in a byte

Robert

(Posted 2005) [#1]

Does anyone know how to shift bits to the left or right in a byte so that they 'wrap'

eg:

1111 0000

shifted to the left 4 times would give:

0000 1111

The shl and shr operators 'lose' any bits that fall off the left or right side respectively.

WolRon

(Posted 2005) [#2]

Nope. Guess you just have to write a function to do so.

ImaginaryHuman

(Posted 2005) [#3]

Umm ....

Local Number=%11110000 '(Is this a binary number, I forget if % is right)
Local Number2=Number
Local BitPlacesToShift:Int=2
Number:Shr BitPlacesToShift
Number2:Shl 8-BitPlacesToShift
Number:|Number2

Something like that, the manual way. This is only for a right shifting roll, you'd probably need another version to move left.

Robert

(Posted 2005) [#4]

Thanks AD, I'll have a look at that later.

Somewhat better than the awful, awful hack that I came up with:

Local b:Byte=2
Local nb:Byte

shift=2

For i=0 To 7
	If (b & Int(Ceil(2^i))) nb :| Int(Ceil(2^(wrapBit(i,shift))))
Next

Print Bin(b)
Print Bin(nb)

Function wrapBit(bitIndex,bitShift)
	bitIndex :+ bitShift
	If bitIndex > 7 bitIndex = (bitIndex-8)
	Return bitIndex
End Function

Ahem.